Oh, Mercy Me!
by Runty Grunty
Summary: Mercy has a little lab accident when Tracer comes over for a visit, one that results in a very special night for the two heroines. F/F Yuri Smutfic.
I'm spreading my smutty horizons a bit tonight. Instead of updating my Bathhouse of Legends or Bathhouse XXX, I'm giving you a special oneshot for the upcoming MOBA shooter Overwatch! I hope you'll enjoy this fic as much as I enjoyed writing it.

For tags, this one is a yuri fic with sex toy use, breast expansion, and lactation. Yum!

Enjoy!

* * *

 **Oh, Mercy Me!**

Mercy, also known as Angela Ziegler, made a short smile as she carefully mixed a series of chemicals for one of her experiments. There was no one else in the lab, and though she usually did work with others for such things, this experiment went outside what most medical professionals would deem appropriate. It was, after all, meant to be used in her work as a modern heroine.

Ever since the enactment of the Petras Act, Mercy had found it difficult to conduct experiments to create newer medical stimulants. Many other respected doctors declined to work with the former Overwatch agent out of fear of being caught up in any legal debacles she might get into. She didn't hold it against them; in fact, she didn't want them to get into any trouble on her account. Still, lack of equipment, funds, and other necessities always made it harder for her.

It was times like this that she actually missed being a part of Overwatch. Despite their more militaristic approaches, they still had a highly advanced science crew when she was around. And beyond their scientists, she also missed the friends she made in Overwatch.

She especially missed a certain brown-haired, hyperactive pilot the most.

She shook her head for a moment before turning her focus back to the task at hand. Her current formula had to be mixed carefully. Normally such a procedure would be left to machines, but she lacked the appropriate equipment in her private lab. She would have to do it manually, and would have to do so without distractions.

Just as she began pouring one beaker into another she almost jumped on her stool as she heard the intercom blaring loudly. Someone had tripped her security system.

But in that instant, the alarm quickly became the least of her worries. In her startled jolt, her grip slipped on the beaker she was holding, which crashed onto the table and shattered into a million pieces, sending its contents splattering all over the place. Almost immediately, the liquid began to release a cloud of pink gas, one that she couldn't avoid breathing in. Stumbling back in surprise, Angela shrieked as she slipped and fell to the floor, her head striking a nearby countertop as she toppled over.

Before she blacked out, she could swear she heard a familiar British accent calling her name.

...

Tracer, a.k.a. Lena Oxton, was almost panicking by now. She had just shown up at Mercy's place to pay the doctor a friendly visit (and accidentally triggering an alarm in the process that had thankfully gone silent by now) when she found her unconscious on the floor, her lab in disarray. Tracer had immediately brought Mercy to her bedroom and tried to stir the blonde medic. She didn't appear to be badly hurt, but the bump on her head wasn't making Tracer any less apprehensive.

Just as Tracer began to contemplate calling a local hospital (something that was sure to open a proverbial can of worms for too many reasons to count), she heard Mercy stir with a soft moan. In a flash of blue, Tracer immediately blinked to Mercy's side.

"Ange? Ange, are you alright?" asked Tracer.

Mercy's eyes slowly fluttered open as she regained consciousness, with Tracer's exuberant smile being the first thing she saw.

"L-Lena? Lena, what are you–"

"Oh, thank goodness, luv!" Tracer said happily. "I found you conked out on the floor and thought you were seriously hurt! What happened to you?"

"S-Someone set off m-my security alarm while I was working on an experiment. I should have been more careful."

"Oh… Umm… Promise you won't be mad if I say I might've–"

"Lena, its fine… Just please, use the front door next time."

"Umm, yeah, sorry about that."

Mercy slowly began to push herself up as she said, "I had a little accident in the lab when you came in. Spilled a few things…"

"Oh… Is that serious?" Tracer asked as she bit her lip.

"I hope not. I should run a bio-scan on myself to make sure, but I'll need your– NNGH!"

Mercy suddenly winced as a jolt of heat and slight pain shot through her chest.

"Ange? Ange, what's wrong?" Tracer asked in fright.

"I-I feel hot… Chest feels… feels tight… I… Nnh… Aahn!"

Mercy yelped again as she wrapped her arms around her chest, this time from a surge of unexpected pleasure. Her cheeks were starting to turn bright red.

Then, just as Tracer was about to suggest taking Mercy to a hospital, the British heroine looked down at Mercy's chest and gasped.

"Umm, Ange? Were you always this… big?"

"H-Huh?" Mercy was left completely baffled by this question.

Looking up, she saw Tracer making a small gesture with her hand, pointing down. Mercy looked down again, and what she saw made her eyes widen in shock.

Her breasts were growing. And they were growing FAST!

"W-W-What?!"

Now she realized why her chest felt so tight. Her breasts, normally a modest C-cup, were quickly testing the limits of her form-fitting lab-suit, stretching the fabric far beyond its normal capacity. She quickly pressed her hands to her chest, as if to try and stymie this sudden growth, but it had no effect. In fact, all it served to do was send another jolt of pleasure through her, making her release an unintended moan.

Sitting next to her and watching Mercy's chest expand, Tracer's look of awe and surprise suddenly gave way to snickering and a failed attempt to withhold a fit of mirth. Mercy was dismayed as Tracer burst with laughter, the British heroine falling back as she held her sides.

"L-LENA! This– NNGH! This isn't funny!" Mercy said indignantly, but her moan of pleasure made the statement fall flat.

"I-I-I'm sorry, Ange! It's just– This is too–" Tracer couldn't continue before bursting out in another hysterical fit.

Mercy scowled at this as she made another grunt of pain, looking back down to see her chest was continuing to expand rapidly. They had easily passed a G-cup by now, and showed no signs of stopping there. Her lab-suit was past its limits, and now was constricting her chest so tightly it was becoming painful. At least it wasn't her Valkyrie armor, Mercy thought; her ribs would likely have been crushed if she were wearing that right now.

"T-Tight…! Too tight…!" Mercy gasped, now finding herself short of breath.

Looking back up with tears of laughter in her eyes, Tracer said, "Oh wow, they're a real handful now!"

"L-Lena, h-help! It's h-hard to breathe!" Mercy said as she tried to pull down the zipper at the back of her suit. Unfortunately, the zipper had gotten stuck from all the stretching.

"S-Sorry, sorry. Here, I got you, Ange."

Tracer brought herself upright and quickly moved to try and unzip Mercy's suit. Unfortunately, she had no more luck with the zipper, which was now completely stuck. Just as Tracer thought to break the zipper, the two heard a ripping noise.

"Oh– Oh no…" Mercy gasped, looking down at her chest.

The suit had begun to tear in the front. The doctor's smooth skin and the front of her lacy white bra were now slightly visible from the tear in the front of her suit. And that tear was slowly widening as her breasts continued to grow.

Tracer made a short "hmm" before adding, "Well, it'll be ruined anyway. Hope you don't mind!"

"Mind wha– EEEHHHHHH?!"

Mercy yelped loudly as Tracer slid her fingers into the tear and ripped open the suit, shredding it from side to side all the way down to Mercy's navel. Mercy's breasts jiggled as they were freed from the suit, but still were barely trapped within Mercy's silky white bra. Said undergarment was tightly clenching her tits, but looked about to break as well.

Thankfully, Tracer didn't even ask before she reached behind Mercy and unbuckled the clasp of the bra. The undergarment was sent launching away from Mercy, and her now-enormous breasts bounced happily free from confinement.

"L-LENA! That was an expensive suit!"

"Sorry 'bout that, luv. But look on the bright side: Not so tight anymore, is it?"

"I-I suppose not, but… this is just… so embarrassing…"

Tracer made a short smirk as she looked back at Mercy's still-expanding boobs. A G-cup was now small compared to them, the mounds of flesh each having grown bigger than Mercy's head, but thankfully their swelling seemed to be slowing down now. Within another minute, Mercy's chest stopped its growth, putting her somewhere near an O-cup.

"Oh my…" Mercy said in dismay. "S-So heavy…"

The doctor, now suddenly realizing the weight of her enormous bosom, placed both hands beneath them to try and hold their weight up. In doing so, however, she felt a surge of hot pleasure jolt through her, almost making her moan loudly again.

Seeing Mercy quiver in near-ecstasy, Tracer said, "Yikes…"

"Oh, what am I going to do?!" Mercy then said in some despair. "I can't be seen like this! I'll become a laughing stock!"

"D-Don't worry, luv. We'll fix this. And don't fret; I'll stay here as long as you need me!"

"R-Really?"

"Anything you need, I'm here for ya.

Tracer nodded affirmatively with a reassuring smile on her face, one that made Mercy sigh with relief.

Then, with a look of uncertainty, Mercy said, "Well, as long as you're offering…"

"What is it?"

"I… I don't know how else to put this, so I'll just come out and say it… Can you… Can you rub my chest?"

"EEH?!"

Tracer's expression turned to confusion and shock as she broke out in a sweat. Her friend, Mercy, had just asked her to grope her?!

"T-They're just so… I need you to… to touch them. Please… Just help me… Feel good…"

Tracer began to laugh nervously at this. Sure, she had found the whole thing hilarious at first, but Mercy's desperate tone was now making it super awkward. Mercy was a good friend, and Tracer was "highly appreciative" of female company, but Angela just wasn't into women like Lena was. She had never made a move on Angela out of worry that she might take it the wrong way.

"Uh, umm, well… I suppose I could… I guess… Ehehe…"

"I-I'm saying you c-can have me, Lena… I need you to h-help me d-deal with these urges… Please… T-Take me…"

Tracer hesitated for a moment, but then nodded and said, "Okay, luv…"

Mercy smiled and then leaned back toward Tracer, shutting her eyes as Tracer experimentally touched her enlarged left breast. As Mercy let out a moan of pleasure to Tracer's touch, the heroine became bolder and grasped both tits in her hands. Mercy gasped loudly as Tracer sunk her fingers into the pliant titflesh, lifting and rubbing her breasts in circles. Tracer made a short 'hehe' as she then pinched Mercy's nipples, which had grown quite erect in all the mayhem. With a short twist of Mercy's teats, the doctor made a loud yelp of ecstasy.

"Oh… Oh yes… That's good…!"

"Like that, do ya? Well I'm just getting started!" said Tracer, her confidence now returning in full.

Releasing her hold on Mercy's left breast for a moment, Tracer raised her hand to cup Mercy's chin and turn her to face her. Mercy was made to stare Tracer in the eye for a brief moment, the doctor's gaze clouded with lust. Tracer was now certain she wanted this.

And with that certainty in hand, Tracer swiftly moved in for a deep kiss.

Mercy was confused out of her mind. She wasn't much of a lover, having never pursued a serious romantic relationship before, and she certainly had no experience with other women in this manner. But Tracer, it seemed, was a pro, and as their mouths connected, Mercy could not help but feel this whole thing was so… right. It didn't feel wrong at all. And she wanted more.

As the two separated for air, Mercy gasped, "L-Lena… you– Aah!"

Sneakily, Tracer had slinked a hand down Mercy's navel and slid underneath the doctor's torn suit, reaching down into her pants. Within moments, the heroine had found the doctor's folds, and found to her delight that they were soaking wet.

"Ooh, you're really wanting this, Ange," said Tracer, shortly before she began to nibble on Mercy's ear.

The gesture made Mercy gasp again in desire, the doctor now grasping her left breast in her own hand while Tracer continued to fondle her right tit. Mercy's right hand now was holding Tracer's hand in her pants, trying to guide it to her most sensitive spots. But it seemed like wherever Tracer touched, Mercy's sensitivity went crazy. She was just so skilled.

"Oh, Lena…! Th-That feels so good! Y-You're so… AAAHN…!"

Tracer smiled in delight at this, happy that Mercy was enjoying herself so much. Licking her lips, Tracer lifted Mercy's heavy right breast to her mouth and wrapped her lips around the erect nipple, sucking hard on it. And at the same time, her fingers, which had just been teasing the folds of Mercy's pussy, plunged into her soaking depths. This made Mercy's eyes shoot wide open, and she almost screamed in joy.

"A-AHH! YES! AH-AAAHHH!"

Tracer began to chew on Mercy's taut nipple as Mercy gasped for breath amidst her screams. Holding Mercy's right breast up by her teeth, Tracer slinked her hand around to fondle the left breast, with both of Mercy's hands trying to push Tracer's invasive fingers deeper into her core.

Tracer then decided to call on a trick of hers for this kind of fun. The Chronal Accelerator whirred to life as she triggered its power, accelerating her body to increased speeds. For a moment, Mercy was worried about what Tracer was doing, but then her screams reached a whole new level of intensity.

Tracer's hands moved with great speed as the Chronal Accelerator sped her up. Mercy's enormous breasts bounced about rapidly as Tracer's right hand rapidly moved between them, squeezing and groping them so much Mercy thought they might bruise. As for Tracer's left hand, her fingering sped up to an almost blinding pace, one such that Mercy was almost unable to catch her breath as she screamed and screamed in absolute bliss.

"OH GOD! OH GOD, LENA! I'M– I'M GOING TO– AAAAAAAAAHHHHHH!"

Mercy wailed loudly as orgasm crashed through her system. Spurts of vaginal fluids burst from her quivering pussy and, to both Tracer's and Mercy's surprise, jets of thick creamy milk were beginning to spray from Mercy's huge tits.

"W-What the? Hey, you aren't… are you, luv?" Tracer asked in some confusion.

Mercy could not answer Tracer's question, too shocked by her massive orgasm. Heavily gasping for air, Mercy fell forward away from Tracer and slumped onto her bed, lying on her back in a daze. Her breasts were still dripping with milk, but Mercy wasn't in a state of mind to care, her thoughts having nearly pulled a whiteout from her intense climax.

Sitting next to her, Tracer brought her sticky left hand up and took a small lick of the vaginal juices that still clung to her fingers. She smiled; Mercy tasted like strawberries, it seemed.

"Like that trick, luv?" Tracer asked cheekily.

Mercy didn't respond, still reeling from Tracer's accelerated fondling.

"Maybe I shouldn't have done that one so early. Oh well, we're not done yet. Do you need a minute?"

Mercy looked up at Tracer for a moment, still gasping for air, but then said in a tone of lust, "M-More…"

"Hmm, she wants more, she says. Then more you shall get, Ange."

Tracer lowered herself onto all fours as she crawled on the bed toward Mercy, the doctor still in the shreds of her lab-suit and her breasts still the size of watermelons. Tracer straddled the doctor's waist as she took those two melons in hand again, pinching her nipples and rubbing them in circles. And with each small squeeze, more milk continued to spurt out.

"Ever thought of being a mum, Ange?" asked Tracer as she lowered herself to Mercy's teats and took a quick lick of her breast milk.

"I… I don't know, Lena…" said Mercy. "If… If only our world were a safer place, then perhaps I'd– NNGH AHH!"

Mercy moaned again as Tracer brought both teats together and began to suck on them, drawing precious milk out with each squeeze given to her heavy breasts. It truly did make Mercy feel like a mother at the time, as though she were feeding a baby her milk. It was just that this baby could manipulate her time and had inexhaustible energy.

Taking a brief break from suckling on Mercy, Tracer asked, "So, how exactly are you making this stuff? You didn't get knocked up by some lucky bloke recently, did you?"

"N-No, of course not," answered Mercy. "It-It must just be a side effect of the s-stimulants. Lena, p-please, keep going."

Mercy took hold of her massive mammaries as she said this, urging Tracer to keep suckling her milk. Tracer could only smirk as she dove forward and planted her lips around both of Mercy's nipples at once.

"Ahh! _G-Gott in himmel…_ "

For a couple of minutes, Tracer continued to suck Mercy's teats, leading to further moans and gasps from the Swiss doctor. But soon, as Tracer stopped for a breather, an idea popped into her head.

"Say, Ange, you're still… untouched down there, right?"

"What?"

"I'm asking if you've never had a 'first time' yet, silly."

"Oh! N-No, I… I haven't yet…"

"Well… feel free to say no, but I was wondering… as long as we're going at it like rabbits, you don't suppose you'd mind if I was your first?"

"H-Huh? B-But you're a woman…"

"Not a problem, luv! Back in a jiff!"

Within literally one second, Tracer had sped off to one side of the room, which Mercy finally noticed had Tracer's duffel bag resting in a corner, and sped back to Mercy. In Tracer's hand was something that shot Mercy's eyes wide open: a strap-on with a rather complex-looking dildo attached to it.

"W-What the? Wait, you carry that in your duffel bag?!" Mercy asked in disbelief.

"Always be prepared, hehe!" Tracer answered cheekily. "Never know when I might need some 'me' time."

"Um… right…"

"So, yeah, it's up to you, but if you're up for it–"

Before Tracer could finish, Mercy had grabbed the heroine, pulled her in, and planted a deep kiss to Tracer's mouth. Tracer was a little surprised by Mercy's boldness, but immediately reciprocated the kiss.

As they separated, Mercy said in a lustful tone, "Do me. I-I need you in me!"

"Really? You sure, luv?"

"Lena, j-just shut up and… and fuck me!"

"Y-Yes ma'am!"

Tracer smiled brightly as she swiftly attached the strap-on to her, giving it a little flick with her finger to ensure it was working. This model was actually a top-seller on the adult market, as it allowed its user to experience the sensations of putting their 'fake dick' into someone's waiting cunny. It was a real hit among 'futanari' fans, and Tracer had used it more than a few times before.

In the meantime, Mercy was trying to pull herself out of the shreds of her lab-suit, but the sweat that clung to her body made the task more difficult than it should have been. Tracer realized the trouble Mercy was having.

"Do ya mind if I just rip it off, luv?"

Mercy paused to think for a moment, and then said, "Oh, go ahead. It's ruined anyways."

Tracer made a few chuckles of appreciation as she grabbed hold of Mercy's suit and tore it open between her legs, revealing Mercy's soaking pussy and drenched panties. Like her bra, they were also a silky white lace, which Tracer opted to push aside rather than tear off. Even if she had already shredded Mercy's lab-suit, she didn't have to do the same to her unmentionables.

As Tracer lined her fake shaft up with Mercy's waiting entrance, the heroine looked to the doctor, who gave a nod of permission. And with that, Tracer thrust her way in, and Mercy screamed as loud as she could.

"You alright, Ange? Does it hurt?"

"A-A little, yes, but please… don't stop now!"

"Hehe, roger that!"

With that, Tracer slowly began to pull back, noting the faint blood stain on her strap-on as she withdrew. Mercy really was a virgin, and the realization only spurred Tracer onward as she slammed back into Mercy's pussy, releasing another scream of desire from the doctor. Within moments, Tracer established a steady rhythm of thrusts that began to drive Mercy to heights of pleasure she had never known before.

Mercy was stunned by how good this all felt. Tracer was so deep inside of her, and whoever had designed her strap-on had clearly done a good job. Despite being artificial, it was almost as if she could feel the faux shaft pulsing within her. Each hard thrust from Tracer made Mercy's unconstrained breasts bounce and jiggle, with trickles of breast milk still leaking down her gigantic globes.

Tracer, on the other hand, couldn't get enough of how tight Mercy was. The strap-on she wore let her feel the sensation of Mercy's vaginal walls clutching hard around the artificial cock, a feeling she swore she would never get tired of. She hadn't had the time for sex in a good while now, and now that she was fucking Mercy she didn't want to stop. She reached for Mercy's boobs and gave the swollen mounds a hard squeeze, to which Mercy made another shout of desire that Tracer took as a sign to continue.

"L-Lena, you're so good! Harder! HARDER!"

"Hmm? Can you say pretty please?"

"P-P-Please, Lena… I-I want you to fuck me harder!"

"That's more like it! Now let's get to the good part!"

Once again, as Tracer brought herself upright and grasped Mercy's hips, her Chronal Accelerator spun to life as her body accelerated. This time, Tracer's thrusts increased in speed, moving so fast that Mercy felt like she was being torn apart.

And it felt so good that she could not stop screaming at the top of her lungs.

"OH LENA! OHHH! LEEENNNNAAAAA! IT'S SO GOOOOOOOD!"

"Lovin' it, aren't you, Ange? You and m-me both! You're so t-tight!"

"L-LENA, I'M– I'M GONNA– I'M GONNA– AAAAAAAHHHHHHHHHHHH!"

Mercy screamed as tears of joy streamed down her face, her body again surging in climax. Spurts of vaginal fluids began to squirt from her pussy as Tracer continued thrusting at hyper speed. But as Mercy's insides clenched around the faux cock attached to Tracer, she found the pleasure overwhelming.

"A-A-AAANNNGGGEEELLLAAA!" Tracer howled as she came as well.

Tracer's spandex was soon soaked between her legs, a mixture of both Mercy's juices and Tracer's own orgasm. The heroine's body shook as she struggled to remain upright, her climax leaving her about to collapse.

A second later Mercy, who was reeling from her second orgasm, made a short choking sound as she felt something spray from Tracer's strap-on into her womb. But the orgasm had left Mercy so exhausted that she couldn't even voice in protest to Tracer somehow cumming inside her. Her vision swam before her as Tracer collapsed on top of her enormous bosom, and Mercy found herself drifting off again into unconsciousness.

...

Chirping birds signaled the new day as Mercy stirred from her sleep. She felt sore all over, especially within her core, the memories of the past night a blur for her. But as her consciousness returned, she remembered the time Tracer had given her. Looking down at herself, Mercy saw she was now stark naked beneath her sheets and, to her relief, her breasts had shrunk back to their normal size. It seemed the effects were only temporary.

But then she remembered the moment right before she blacked out. Tracer had released… something inside of her! Mercy's hand went to her navel, almost in a fit of panic.

"Mornin', luv!"

Mercy abruptly turned to face Tracer. The heroine was dressed far more casually than she had been last night, her spandex replaced by a large nightshirt and nothing else besides her Chronal Accelerator harness.

"G-Good m-morning, Lena," Mercy said in response.

"Have a good sleep, Ange?"

"You could say that…"

"Hmm? Is something wrong?"

"L-Lena, I really enjoyed last night, b-but you…" Mercy didn't finish, instead placing a hand to her navel in a gesture to show what she was talking about.

"Oh, you're worried about getting knocked up? Don't fret, luv. It was just water. I fill that thing sometimes from the tap just to make the end feel better."

Hearing this, Mercy sighed loudly in relief. She wasn't ready to be a mother yet.

"Sorry if I spooked you, Ange. I'll ask next time."

"N-Next time?"

"Of course! That was some of the best snoggin' I've had in a while! You've got to figure out how to repeat that, big boobs and all!"

Mercy couldn't find anything to say to Tracer's request, instead only laughing nervously as her face turned a bright red.

* * *

Oh Tracer, you lovable spunky thing!

I look forward to playing as her in May during the Overwatch open beta. I hope to see you guys there!

Please leave reviews!


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